It is hard to imagine escrowed encryption schemes working as their advocates imagine without some kind of legal pressure. The obvious next step is a ban on the use of non-escrowed encryption. This is probably the only way to make a commercial system pay, and its certainly the only way to get technologically sophisticated criminals and terrorists to use it. Its not clear how difficult outlawing non-escrowed cryptography will be, or how it will affect cryptography as an academic discipline. How can I research software-oriented cryptography algorithms without having software non-escrowed encryption devices in my possession; will I need a special license?

And there are legal questions. How do escrowed keys affect users liability, should some encrypted data get out? If the U.S. government is trying to protect the escrow agencies, will there be the implicit assumption that if the secret was compromised by either the user or the escrow agency, then it must have been the user?

What if a major key-escrow service, either government or commercial, had its entire escrowed key database stolen? What if the U.S. government tried to keep this quiet for a while? Clearly, this would have an impact on users willingness to use key escrow. If its not voluntary, a couple of scandals like this would increase political pressure to either make it voluntary, or to add complex new regulations to the industry.

Even more dangerous is a scandal where it becomes public that political opponent of the current administration, or some outspoken critic of some intelligence or police agencies has been under surveillance for years. This could raise public sentiment strongly against escrowed encryption.

If signature keys are escrowed as well as encryption keys, there are additional issues. Is it acceptable for the authorities to use signature keys to run operations against suspected criminals? Will the authenticity of signatures based on escrowed keys be accepted in courts? What recourse do users have if the authorities actually do use their signature keys to sign some unfavorable contract, to help out a state-supported industry, or just to steal money?

The globalization of cryptography raises an additional set of questions. Will key-escrow policies be compatible across national borders? Will multi-national corporations have to keep separate escrowed keys in every country to stay in compliance with the various local laws? Without some kind of compatibility, one of the supposed advantages of key-escrow schemes (international use of strong encryption) falls apart.

What if some countries dont accept the security of escrow agencies on faith? How do users do business there? Are their digital contracts upheld by their courts, or is the fact that their signature key is held in escrow in the U.S. going to allow them to claim in Switzerland that someone else could have signed this electronic contract? Or will there be special waivers for people who do business in such countries?

And what about industrial espionage? There is no reason to believe that countries which currently conduct industrial espionage for their important or state-run companies will refrain from doing so on key-escrowed encryption systems. Indeed, since virtually no country is going to allow other countries to oversee its intelligence operations, widespread use of escrowed encryption will probably increase the use of wiretaps.

Even if countries with good civil rights records use key escrow only for the legitimate pursuit of criminals and terrorists, its certain to be used elsewhere to keep track of dissidents, blackmail political opponents, and so on. Digital communications offer the opportunity to do a much more thorough job of monitoring citizens actions, opinions, purchases, and associations than is possible in an analog world.

Its not clear how this will affect commercial key escrow, except that 20 years from now, selling Turkey or China a ready-made key-escrow system may look a lot like selling shock batons to South Africa in 1970, or building a chemical plant for Iraq in 1980. Even worse, effortless and untraceable tapping of communications may tempt a number of governments into tracking many of their citizens communications, even those which havent generally tried to do so before. And theres no guarantee that liberal democracies will be immune to this temptation.